RPM Drop From Nuetral to Gear

I seem to be having a heck of a time tuning the 340 in my Dart. It seems to run great in park, but as soon as I drop it in gear, RPMs drop from about 900 to about 500 and kills the engine. The only way I can get it to run in gear is to bump the idle past the transition slots in the carb which nullify the idle mixture screws.

I realize I need to address the timing first, but here's the basic combo: 340, torker intake (soon to be RPM airgap- will swap intakes this weekend), 750 Holley DP, convertor is likely stock but unknown, 727, 3.91s, 28" tire.

As for the cam- that's another unknown. I was told when I bought it, that it's a MP purple shaft, but I'm not sure which one. It's likely either the 280* or 284* hydraulic flat tappet. Do you think the stock convertor may be to tight for either of these cams?

This motor seems to love a ton of initial timing. I set it at 22* initial and it starts fine and wants more. Weird??? I set the timing in Park, but will check it in gear this weekend if I can get it to even run in gear. When I set the timing, it seems to bounce around at idle too. Is this a sign that the springs are too soft??? I'm using a MP orange box and new adjustable MP distrib. Not sure what springs are in it, but will have a look this weekend as well- they may have been changed by the previous owner.

So, what should be my plan of action?? I know I need to nail down the timing first, but how should I go about it if I can't even get it to idle in gear? I have extra butterfly throttle valves for my carb. Maybe drill a couple holes in them to help me get this thing to idle in gear??

Thanks for all the help guys. I realize I'm being really ignorant by asking these basic questions, so make fun all you want. :prayer: I just want to drive this thing.